Representative sampling and dilution is advantageous when using instruments to analyze a process flow in order to accurately study the process fluid or slurry. A dense slurry can prevent signals, such as laser, visual, infrared or ultraviolet light, from penetrating the mass of particles. As a result, a corresponding sensor is unable to receive the signals in order to analyze the particulate features including, for example, size, shape and quantity. By diluting a representative sample of the process flow, the signals can penetrate the fluid or slurry and accurate signals can be obtained and analyzed. If the sample is representative, the analysis will present an accurate characterization of the process flow as a whole. Being able to dilute the fluid or slurry at the flow line allows the process flow to be analyzed in a timely manner. If the sample removed and taken to a lab for analysis, the process requires considerable manpower and time, both of which are disadvantage. Moreover, the time required for lab analysis typically prevents the possibility of obtaining real time results. Due to the delay in performing lab analysis, the characteristics of the process flow can change considerably before the analysis is known. is critical in analyzing a process in a timely manner. During this time, if unfavorable conditions exist, it is possible for the process to proceed to an out of control condition.
Many flow analysis systems use a sample from a single point in the process flow. However, such point sampling can lead to several errors. First, due to the possible stratification of the flow in the line, the point sample is unlikely to be an accurate representation of the flow. This is particularly true for slurries, where the weight to lift ratios of the particulates can result in varying characteristics of the flow across the line due to gravity. Further, the piping configuration itself can cause the flow to stratify so that the point sample is unlikely to be representative of the entire flow. In addition, the types of samplers used to provide a point sample of the process flow often exacerbate the problems associated with stratification of the flow. The structure of the sampler within the flow line may lead to changes in the fluid velocity within the flow, which will lead to further stratification of the flow. Lastly, the sampling tube devices that are often used for point samples can change the velocity of the sampled fluid which also leads to stratification and may cause heavier particles to drop out of the sampled flow and be excluded from the sample entirely. This iso-kinetic characteristic of a drawn sample is always of concern when trying to achieve a representative sample.